Neuromodulation is a method of treating pain symptoms by therapeutically altering activity in pain pathways with the use of an implantable device. Neuromodulation works by either actively stimulating nerves with electrical energy to produce a natural biological response or by applying targeted pharmaceutical agents in small doses directly to a site of action.
Electrical stimulation involves the application of electrodes to the brain, the spinal cord or peripheral nerves of a patient. These precisely placed electrodes are typically mounted on a lead that is connected to a pulse generator and power source, which generates the necessary electrical stimulation. A low-voltage electrical current passes from the generator to the nerve, and can either inhibit pain signals or stimulate neural impulses where they were previously absent. One of the most common types of electrical stimulation is spinal cord stimulation (SCS), which has been used as a treatment option for patients with chronic pain since the 1960s. In the last 30 years, it has become a standard treatment for patients with chronic pain in their back and/or limbs who have not found pain relief from other treatments. While the treatment does not work for everyone, many patients who qualify for neurostimulation therapy receive a reduction in overall pain. Some patients find that they can decrease their pain medication after undergoing spinal cord stimulation. Given these benefits, many individuals suffering from chronic pain find that neurostimulation positively impacts the quality of their lives.
In some instances, neuromodulation can alternatively been achieved by delivering pharmacological agents through implanted leads or catheters. In this manner, the agent can be administered in smaller doses because it does not have to be metabolized and pass through the body before reaching the target area. Smaller doses—in the range of 1/300 of an oral dose—can mean fewer side effects, increased patient comfort and improved quality of life.
However, neuromodulation is not without its risks and complications. One complication associated with the implantation of leads is lead migration which can cause loss of effective stimulation over time. During migration, the stimulation electrodes, typically at the distal end of the lead, move in relation to the nerve creating a less desirable stimulation effect. Traditional SCS leads are positioned within the epidural space which is a largely unconfined area. In addition, such leads are typically anchored outside of the epidural space, such as to the fascia above the supraspinous ligament or to the supraspinous ligament itself. Consequently, the portion of the lead distal to the anchor is free to move along the entire length of the lead from the point of anchor to the tip in any direction within the epidural space. Such movement can reposition the lead such that stimulation is altered or even negated over time. Similarly, catheters positioned within the epidural space can also suffer from migration leading to agents being delivered outside of the target location,
Movement or migration of the lead can be caused by: 1) body motions (flexion, torsion, and so on); 2) tensile force transferred to the distal end of the lead from the proximal portion of the lead (i.e. from the anchor IPG connection point, or fascia, or ligaments); 3) gravity settling of the lead body; and/or 4) other factors. An anchor or other means to prevent migration is intended to prevent or reduce motion of the distal end of the lead due to these causes.
Improved anchoring of leads and catheters are desired. Such anchoring should be noninvasive to avoid damaging or harming the patient anatomy, particularly delicate nerve tissue and, in some instances, reversible so as to allow a revision of the system without having to access the epidural space directly to remove the lead. At least some of these objectives will be met by the present invention.